Voltmeter pegged after battery reversed

[Siphon]

Yeah, moment of rushing and stupidity took hold and I reversed terminals on the starting battery. The boat is an 01 Sea Ray 210 Sundeck 5.0 Merc Alpha with dual batteries, on a 1/2/both switch with an isolator.

Replaced the alternator, batteries, and put in a new Blue Sea switch and ACR.

The good news is the boat fired right up and ran great.

The bad news is with the boat running my voltmeter is pegged (top of the gauge is 16 volts). At first I thought I’d just blown the gauge but then I shut the motor off and it dropped back to the bottom.

Any help would be much appreciated!

 

[Bt Doctur]

Replace the alt

 

[Siphon]

Did that.

 

[GA_Boater]

Check your wiring.

 

[alldodge]

Assuming your talking about the helm voltmeter and not a hand held, it might be the gauge. Check with a hand held, and if it reads the same 16V, then it could be the since lead (Red/Purple) is disconnected.

With ignition OFF, see if there is 12V on the Red/Purple wire at the ALT. Then measure the purple wire at the ALT with key OFF there should be zero volts. Now turn key ON and the purple wire should read 12V

 

[Siphon]

Yes, the helm voltmeter.

Thanks, I’ll check it at the gauge and at the alternator voltage regulator. Hard to imagine it would be bad since it’s brand new.

I guess it could be reading high if the batteries somehow got wired in series, but I thought the whole point of the Blue Sea setup was to truly separate them.

 

[alldodge]

An ALT will run full out voltage if the since lead is not connected (this is what I'm wondering). You had a reverse polarity connection, son wondering if the connection was severed

Oh just thought of something else, see if you have battery voltage on the orange wire on the ALT. Might have blown the 90 amp fuse

 

[Siphon]

Ok, I think it’s just the gauge. With the key on it now reads about 15v but shows normal 12.5 across the terminals at the back. The alt seems to be right. With the key off at the pink/green wire I’ve got 12.3V and no volts on the purple wire. Purple shows 12.3V with the key on.

With the engine running I show 14.3-14.6V everywhere — alt, ACR, and battery terminals — the back of the gauge reads that same range but the needle is pegged over 16.

So, thanks for helping me track it down!

While I was under the helm I could hear a relay or solenoid clicking open and closed. Click-click, then silence for 30 seconds or so. Then click-click. Key was on but engine not running. Any ideas?

 

[alldodge]

I would guess that was the hour meter in the Tach

 

[mike_i]

some volt meters don't have reverse polarity protection, which is nothing more than a diode, so reversing polarity will blow the meter, I agree with alldodge, you're hearing the hour meter ticking.

 

[Siphon]

Would the hourmeter still be clicking if the engine isn’t running? Don’t remember it making that noise last season.

 

[GA_Boater]

Key on - Hourmeter runs. That's how the meter tracks hours.

With the key off, you shouldn't hear the clicking.

 

[Siphon]

Thanks, guess I am just hypersensitive about every little thing that could be wrong at this point.

Speaking of which... an update for the morbidly curious — my tach seems to operate normally when the engine is running but now sticks at 600 revs with engine off and all power off. And my temp gauge seems to approximately work until the thermostat opens, then it starts bouncing all around from 180 to 130 and everywhere in between. I guess I fried the whole gauge cluster.

 

[alldodge]

Would say temp gauge has either a bad connection (12V, Gnd, sensor lead) or the gauge is going bad. The tach may just have a ruff spot were it pivots

 

[gwhitten]

Well, Siphon, you are not alone! I wondered why my 2012 Chaparral 190 with 4.3L Mercruiser outdrive wouldn't fire up. I was checking the wiring under the dash when I noticed the -12v reading. Ouch! When I checked the battery, I realized that I had reversed the terminals...ignoring the + on the battery in favor of the red protector that was somehow moved to the negative battery terminal!!!
Tomorrow, I'll begin the process of trying to understand what happened. I do remember seeing a spark when I connected the battery initially. Hopefully, it is a fuse. At the moment, I have no power to the instruments, or the ignition switch, though there is +12v at the dash.

 

[Siphon]

I’m sorry to hear that! If it didn’t let the smoke out on a backward connection hopefully that means your fuses and breakers did their job. My experience has been that the broken things don’t reveal themselves all at once, so it’s good to keep it in the driveway or close to the dock until you’re confident it’s running right.

 

[Fed]

When you turn it off & the tach sticks at 600 try then turning the key back to the run position (not start) & see if the tach goes to zero.

 

[Siphon]

Yeah I had that same thought, but...it doesn’t. I’ll dig back into it this weekend and post an update. Testing the temp gauge function and likely replacing the sender and thermostat. If it’s not that, maybe I have a bad ground somewhere — melted a wire or who knows what. Any thoughts on islolating it would be appreciated.

Aside: also beginning to think I might have a mechanical cooling system problem on top of it all (not getting much water out the exhaust ports), so this will pretty much go down as my longest, most annoying, and stupidest pre-splashdown routine ever.

 

[Siphon]

Temp gauge seemed to test out ok. Sender was bad. Replaced it and the t-stat. Now the gauge behaves more normally, steady rise up to about 170 on muffs. I didn’t see it drop when the t-stat opened and 170 is a little hotter than it would usually run so I don’t have full confidence in it. Also didn’t change from 170 if I took the RPM up to 1200. But at this point I think I’ll just put it in the water and see.

Tach now decided to reset to zero with a key cycle. Still sits on 300-600 RPMs when I first shut it off but drops when I hit the key again. Does seem to be accurate when running.

Thanks for all the help.